## Risk Factors for Osteoarthritis ### Established Risk Factors by Strength of Association | Risk Factor | Strength of Association | Mechanism | |---|---|---| | **Age** | Very Strong | Cumulative cartilage wear; reduced chondrocyte repair capacity | | **Obesity** | Very Strong | Increased mechanical load; pro-inflammatory adipokines | | **Joint trauma/injury** | Very Strong | Direct cartilage damage; post-traumatic OA | | **Female gender** | Moderate–Strong | Hormonal factors; post-menopausal decline in estrogen | | **Smoking** | Weak–Moderate | Unclear mechanism; may impair cartilage healing | | **Vitamin D deficiency** | Weak–Moderate | May affect bone remodeling; not primary driver | | **Sedentary lifestyle** | Weak | Lack of joint movement; muscle atrophy | **High-Yield:** Age and obesity are the two STRONGEST modifiable and non-modifiable risk factors for OA. Together, they account for the majority of OA cases globally. **Key Point:** The "mechanical load hypothesis" explains why obesity and age are so strongly linked—both increase stress on joints and reduce the capacity for cartilage repair. **Clinical Pearl:** Post-menopausal women have a sharp increase in OA incidence due to loss of estrogen's protective effects on cartilage and bone. **Mnemonic — OA Risk Factors (AFOOT):** - **A**ge (strongest non-modifiable) - **F**emale gender (post-menopausal) - **O**besity (strongest modifiable) - **O**ld injuries / joint trauma - **T**rauma and mechanical stress [cite:Harrison 21e Ch 329] 
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